1. Field of the Invention
The present invention relates to an apparatus adapted for use with respiratory equipment and, more particularly, to an exhalation port device with a built-in entrainment valve feature.
2. Description of the Related Art
Pressure support systems that provide a flow of gas to an airway of a patient at an elevated pressure via a patient circuit to treat a medical disorder are well known. For example, it is known to use positive airway pressure devices, such as a continuous positive airway pressure (CPAP) device, to supply a constant positive pressure to the airway of a patient to treat obstructive sleep apnea (OSA) as well as other disorders. It is also known to provide a positive pressure therapy in which the pressure of gas delivered to the patient varies with the patient's breathing cycle or varies with the patient's effort to increase the comfort to the patient. This mode of pressure support is typically referred to as bi-level pressure support. Still other pressure support systems, referred to as auto-titration systems, vary the pressure delivered to the patient based on the monitored condition of the patient, such as whether the patient is snoring, having apneas, etc.
A typical pressure support system comprises a gas flow/pressure generating device that produces a flow of gas and a conduit having a first end portion that is coupled to the outlet of the pressure generating device. The conduit, which is typically referred to as a patient circuit, carries the flow of gas from the pressure generating device during operation of the system. A patient interface, which is typically a nasal or nasal/oral mask, is coupled to a second end portion of the conduit. In a single-limb system, an exhaust vent is provided on the patient interface or the patient circuit to exhaust gas from the patient circuit. A typical exhaust vent is a continuously open port provided in the conduit or patient interface to allow gas to escape from the system to the ambient atmosphere.
Should the gas flow/pressure generating device become dysfunctional, for example as a result of a power outage or other problem, a flow of gas will no longer be delivered to the patient interface. While the conventional exhaust port may provide some fresh gas to the patient, the amount of gas it can provide is typically not adequate to sufficiently ventilate the patient, which may lead to the patient rebreathing their own carbon dioxide.
To address this situation, it is known to provide a valve, typically referred to as an entrainment valve, at or near the patient interface. The entrainment valve functions by providing automatic access of the patient's airway to the ambient atmosphere if the pressure or flow in the gas flow delivery system falls below a threshold level. More specifically, a typical entrainment valve is provided at the inlet of the patient interface and includes a relatively large port that is selectively blocked by a movable element. The moveable element blocks the large port during normal operation because the gas flow or pressure holds the moveable element in place over the large port. If the flow or pressure falls, for example, during a power outage or equipment malfunction, the moveable element is no longer held over the large port, thereby unblocking it and allowing the patient automatic access to the ambient atmosphere through the large port so that he or she receives adequate ventilation. Examples of such entrainment valve are disclosed in U.S. Pat. Nos. 5,438,981 and 5,647,355 both to Starr et al. and in U.S. Pat. No. 6,851,425 to Jaffre et al.
It can be appreciated that these conventional entrainment valve systems require one valve system to provide the entrainment valve function in the event of a pressure loss and a separate valve system to provide the continuous exhaust gas flow function during normal operation. The need for separate components, with separate exhaust paths, complicates the patient circuit and patient interface system, increasing its cost and complexity, and does not efficiently use the space available near the patient.